Conventionally, a mechanical switch is frequently provided to implement a user control interface device. Because the conventional mechanical switch needs to be in direct contact with the user so as to operate in response to the user's control command, the conventional mechanical device tends to have the structural damage during the user's operation process. At present, a touch switch, such as a capacitive switch, is developed.
In order to enhance the convenience in use, a touch panel or a display touch panel capable of displaying information and being touched has been developed. The touch panel or the display touch panel can receive the input operation and the click operation of the user. The touch panel or the display touch panel may be applied to various electronic devices, such as mobile phones. Thus, the user can directly click a frame on the touch panel or the display touch panel to perform the operation so that the more convenient and more human-oriented operation modes can be provided. There are many types of touch panels or display touch panels, and the capacitive touch panel or the capacitive display touch panel is one of them.
When the user operates the capacitive touch panel, the capacitive display touch panel or the capacitive switch, the capacitance of the capacitor under test therein is changed due to the user's operation. Thus, the user's operation can be detected. However, it is an important subject to design a capacitance evaluation circuit capable of effectively detecting the capacitance variation of the capacitor under test and thus to enhance the performance of the capacitive touch panel, the capacitive display touch panel or the capacitive switch.